Neurons in tissue culture should provide a good system for identifying some of the factors involved in producing the malfunctions observed when brain tissue comes in contact with Marijuana products or opiates. In this project, we propose to study the effects of Marijuana (delta 1 THC) and morphine on cerebrum, cerebellum, midbrain spinal cord and dorsal root ganglion from the chick embryo, neonatal mouse, rat and cat maintained in culture. After various periods of exposure with increasing dosage, these drugs will be withdrawn from the medium and replaced with fresh control media. Morphologic, cytologic and neurophysiologic responses in these tissues will be studied with time-lapse cinemicrography and electrophysiology (intracellular and extracellular recording) and with staining techniques during and after the different phases of exposure to drugs. The experiments will be designed to mimic paradigms of tolerance and addiction.